The invention relates to a receiver comprising at least two receive branches for receiving an incoming signal corresponding to a transmitted data sequence, in which the resulting signals of each receive branch are combined in accordance with their receive quality.
Receivers comprising at least two receive branches, each receive branch receiving signals that have equal signal contents, are denoted as diversity receivers. In so-called space-diversity arrangements the aerials of each receive branch are arranged several wavelengths apart. In so-called frequency-diversity arrangements the signals are transmitted and received at different frequencies. Since the transmission requirements are different for each transmission path or each position with respect to frequency, the signals are received with different qualities in the separate receive branches. With a sufficiently large distance between the aerials in a space-diversity arrangement or with a sufficiently large distance with respect to the frequency of the signals in a frequency-diversity arrangement, the receive qualities of the individual signals in the receive branches are even statistically independent of each other. Therefore, by properly processing the signals received in the separate receive branches, it is possible to obtain a received signal that has better properties (e.g. in respect of signal-to-noise ratio) than any of the separately received signals.
In "Microwave Mobile Communications" by William C. Jakes Jr. the concept of maximal ratio combining denotes a processing option of the received signals of a diversity receiver, in which each received signal is weighted in accordance with the useful signal-to-noise signal ratio and the weighted signals are added together to form a single signal.
With maximal ratio combining as far as this is known for analog signals, the phase conditions of the analog signals are to be adapted to each other before the signals are added together. If, on the other hand, the received signals are based on data signals having so large a data rate that intersymbol interference occurs caused by the dispersive channel, the adding together of the separately received signals generally leads to a deterioration of the total signal.